1. Field of Invention
This document relates to a digital rights management (DRM) method for a terminal.
2. Related Art
A digital rights management (DRM) system is a technology for controlling the use of digital content within the scope of contracts between a user and a content provider. DRM may control the usage of digital content such as text, music, images, movies, software, and games which are distributed through various channels.
The DRM system encodes content to be distributed, and permits only a user having a rights object (RO) to decode the distributed content, thereby preventing software piracy such as illegal copy and illegal distribution. The RO is a type of license for using content. The RO includes information such as a content encryption key, permission information, limitation information, state information, and a content decryption key.
Three methods for implementing digital rights management (DRM) have been introduced: Forward-Lock, Content and RO combined delivery, and Content and RO separate delivery. The Forward-Lock method is a technology which permits the user that received digital content to use the received digital content, and prohibits the received digital content from being modified or forwarded. In the Forward-Lock, an authentication key is not used for protecting digital content.
The Content and RO combined delivery method generate and deliver a DRM message, which binds digital content with an authentication key for defining rights for using digital content. Thus, the digital content of the DRM message received by a mobile communication terminal is used according to the rights definition included in the DRM message corresponding to the authentication key.
The Content and RO separate delivery method delivers digital content and a corresponding authentication key through separate messages. Thus, in order to use digital content received by a mobile terminal, an additional message including an authentication key has to be received from the service provider. Further, in the content and RO separate delivery, the digital content is encrypted into DRM content format (DCF). The corresponding authentication key delivered through the additional message is a Content Encryption Key (CEK) or a Rights Object (RO).
The DRM methods to be applied to digital content are selected by a service provider. Further, even if digital content is purchased from the same service provider, properties of ROs may vary corresponding to the scope of the contracts for the digital content purchased by a user. That is, different digital content rights may be assigned to the same content.
According to the conventional DRM system, content selected by a terminal is determined to be a duplicate of stored content if the selected content has a name identical to content previously stored in the terminal, thereby interrupting the download of the selected content. Thus, a user may not download content having a name identical to the name of the previously stored content even though the content has different digital content rights from the digital content rights of the previously stored content.
Therefore, various methods have been introduced that re-name content when the same content is downloaded more that once and is already stored on a terminal. However, these methods inconvenience a user because a user must manage multiple files with different names for the same content.